The gravity station data (1,633,499 records) were gathered by various governmental
organizations (and academia) using a variety of methods. This data base was received
in March 1999. Principal gravity parameters include Free-air Anomalies and Simple
Bouguer Anomalies (with terrain correction applied only in areas where substantial
variations in local topography exist). The gravity station data has been adjusted
to the International Gravity Standardization Net 1971 (IGSN 71) and the gravity anomaly
computation uses the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula.
The data are randomly distributed within the boundaries of the U.S., Alaska and Hawaii.